GoSoapBox

This free (for K-12 and university educators to use with small classes of up to 30 students) web-based clicker tool can be used for polling, questions, and even to learn who is confused (via the Confusion Barometer). Keep students engaged and gain real-time insight into their comprehension of materials. Instructors and learners "join" an event using any device. Responses are anonymous so chances are good that students will submit questions they would never ask in class for fear of being embarrassed.